Handling of petroleum liquids can be challenging, sometimes resulting in accumulation of such liquids beneath petroleum production, transmission, refining, and storage facilities. Petroleum liquids in subsurface environments are referred to as Light Non-Aqueous Phase Liquids (LNAPLs). LNAPLs may impact groundwater quality and indoor air quality, and may migrate into unimpacted soils and/or surface water bodies.
While active releases of LNAPL often expand, once the LNAPL release ceases, resistance to LNAPL flow increases due to LNAPL depletion associated with dissolution and volatilization. Furthermore, forces driving LNAPL migration diminish as LNAPL concentrations in release areas decay. A consequence of increased resistance to flow and decreased driving forces is that LNAPLs tend to become more stable with time. The stability of LNAPL plumes is often a key factor driving decisions for remedial measures at LNAPL sites.
U.S. Pat. No. 7,281,435 for “Measurement Of Non-Aqueous Phase Liquid Flow In Porous Media By Tracer Dilution” which issued to Thomas C. Sale et al. on 16 Oct. 2007, the teachings of which are hereby incorporated by reference herein, describes a single-well tracer dilution technique with continuous mixing used to measure LNAPL stability. The use of tracer dilution methods to measure LNAPL stability is easier and more accurate than estimates obtained using Darcy's equation since limitations on estimates of LNAPL flow using Darcy's equation include: (a) difficulties with accurately estimating formation conductivity to LNAPL; (b) difficulties with estimating the force driving LNAPL flow; and (c) difficulties with the assumptions inherent to field application of Darcy's equation, including an extensive continuum of a homogenous LNAPL.